Thursday, March 1, 2012

Blogging impact on academic papers

This paper linked from this post from World Bank Development Impact blog has been around for a while and it was spread through the blogosphere pretty quick. David Mckenzie and Berk Ozler analysed the effects of blogs on paper’s downloading and results showed that when the blog is widely followed, mentioned papers’ popularity increase dramatically.
Even the model used to measure blog’s impact on papers is simple and nice, in their own words:

“To formally test for the impact of different blogs on abstract views and downloads we put together a database of 94 papers linked to on 6 blogs: Aid Watch (before it ended), Chris Blattman, Economix (New York Times), Marginal Revolution, Freakonomics, and Paul Krugman. We define t=0 in the month in which the blog entry occurred, t=-1 in the month before, t=+1 in the month after, etc. Then we estimate the impact of blog s linking to a paper i via the following regression:

This controls for paper-specific fixed effects, and looks for a spike in views in the month the paper is blogged about, tests whether this continues into the next month, and also includes a lead term to rule out reverse causation whereby a paper gets a lot of downloads for some other reason, leading people to blog about it. For robustness we also include paper-specific linear time trends.”

They summarized their findings as:

• Blogging about a paper causes a large increase in the number of abstract views and downloads in the same month: an average impact of an extra 70-95 abstract views in the case of Aid Watch and Blattman, 135 for Economix, 300 for Marginal Revolution, and 450-470 for Freakonomics and Krugman. [see regression table here]
• These increases are massive compared to the typical abstract views and downloads these papers get- one blog post in Freakonomics is equivalent to 3 years of abstract views! However, only a minority of readers click through –we estimate 1-2% of readers of the more popular blogs click on the links to view the abstracts, and 4% on a blog like Chris Blattman that likely has a more specialized (research-focused) readership.
• There is some spillover of reads into the next month (not everyone reads a blog post the day it is produced), and no evidence that abstract views and downloads lead blog posts.

Graphically, some of the most important economics blogs and its effects on several papers: